Ares's family have always had a hard time with kids. Kronos cursed them to suffer with infertility. Nearly every attempt ended in cruel miserable failure. The few kids that did survive were born weak, in very very painful childbirth. Ares, like the rest of the gods, is incredibly protective of his family. Kids are seen as the most precious thing in the world, a sacred miracle.
Ares has attempted to have kids several times, all ended in misery. Usually the mother would die in some accident, something that could have been avoided. Yet no matter what Ares does they never live till term. None of his children have lived to be born.
When the gods do manage to have kids they have to plan ahead. Meticulously set aside a domain for the new child, to ease the transition and give something for the child to cling to. Even then it often isn't enough. Ares has seen his parents sobbing after losing his potential siblings many, many times. And even when it does work, it's extremely painful and often the child is born weak or only partially formed.
Ares has been polishing his spear when he accidentally cut himself. As the drop of blood touched the ground he suddenly felt his body explode into agony. Agony he recognized from his previous attempts at having kids. But he hadn't planned for this, hadn't set anything aside for the new godling! Fuck, what can he do?! Something, anything, what domain can I break off swiftly?! I can't lose another one, please.